EARLY ESTRUS IN THE CAT FOLLOWING INCREASED ILLUMINATION

Abstract

In the latitude which includes Cambridge, Mass., cats have a normal breeding period usually extending from the middle of Jan. to the middle of July. In 2 expts. conducted in the autumn of 1939 and 1940. early estrus was induced by increased illumination during the anestrous period. In 1939, 4 of 7 cats responded. Lighting expts. were begun on Oct. 25; the first estrus was obtained 49 days later, on Dec. 13, with the last cat exhibiting estrus 13 days later. In 1940, 6 cats were used. They were subjected to decreased illumination for 39 days before receiving the additional lighting. Lighting was begun on Oct. 2; all 6 cats responded. The first animal was observed in estrus on Nov. 21 after 50 days of increased lighting and the last on Dec. 12. Previous shortening of the day apparently did not reduce the time before the response occurred. Although a small number of animals was used, the results are regarded as significant. The intervals of increased lighting preceding the first response were the same in each expt. although illumination was begun 3 wks. earlier in the anestrous period of 1940.